Light source device and projector

ABSTRACT

A light source device includes: a light emitting plate that has a plurality of segment regions including a transmissive portion that transmits light and a reflective portion on which a fluorescent substance layer; a light source that irradiates the fluorescent substance layer of the light emitting plate with the excitation light; a dichroic mirror that is disposed between the light source and the light emitting plate to transmit the excitation light and reflect fluorescent light from fluorescent substances of the fluorescent substance layer; and an optical device that condenses the excitation light transmitted by the transmissive portion of the light emitting plate and the fluorescent light reflected by the dichroic mirror on a single optical path to form a condensed light and radiate the condensed light toward the same direction.

CROSS-REFERENCE TO THE RELATED APPLICATION(S)

The present application is based upon and claims priority from priorJapanese Patent Application No. 2009-155434, filed on Jun. 30, 2009, theentire content of which are incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present invention relates to a light source device and a projectorincluding the light source device.

2. Description of the Related Art

Nowadays, data projectors are often used as image projection apparatusesfor projecting a display image of a personal computer, a video image, animage based on image data stored in a memory card or the like onto ascreen. In such a projector, light emitted from a light source iscondensed on a micromirror display device called a DMD (DigitalMicromirror Device) or a liquid crystal panel so as to display a colorimage on a screen.

Conventionally, use of high-luminance discharge lamps as light sourcesin such projectors has become the mainstream. In recent years, however,there have been many developments or proposals using light emittingdiodes, laser diodes, organic ELs, phosphor emissions, etc. as lightsources. For example, JP-A-2004-341105 discloses a light source deviceincluding a solid-state light source for emitting ultraviolet light asexcitation light and a fluorescent wheel consisting of a disc-liketransparent substrate on which there is disposed a fluorescent substancelayer for receiving the ultraviolet light emitted as excitation lightand converting the ultraviolet light into visible light.

According to the disclosure of JP-A-2004-341105, a visible lightreflective film for transmitting ultraviolet light and reflectingvisible light is formed on a wheel surface of the fluorescent wheel onwhich the ultraviolet light will be incident. Thus, the fluorescentsubstance layer disposed on the emission-side wheel surface isirradiated with the incident ultraviolet light to generate fluorescentlight and emit the fluorescent light to the emission side. At the sametime, fluorescent light emitted to the incident surface side from thefluorescent substance layer is also reflected to the emission side bythe visible light reflective film. Thus, the quantity of fluorescentlight emitted from the fluorescent wheel can be increased.

In addition, in order to prevent optical components from being damagedby irradiation with excitation light, for example, a blue laser diodewhich emits blue wavelength light as excitation light may be used as thesolid-state light source of the aforementioned light source device. Inthis case, the fluorescent wheel is configured to have a diffusion layerformed on the wheel surface so that the blue wavelength lighttransmitted by the fluorescent wheel can be used as it is.

A reflective film for transmitting blue wavelength light and reflectingany other visible light has to be formed on the incident surface of thefluorescent wheel for use in such a light source device. Manufacturingthe light source device therefore becomes labor-consuming, causingincrease in cost.

To solve the problem, a light source device can be conceived to have thefollowing configuration. That is, a wheel substrate is formed out of ametal plate or the like so that blue wavelength light serving asexcitation light and fluorescent light including red and greenwavelength lights and emitted from fluorescent substances can bereflected by a reflective surface of the metal plate. Thus, blue, greenand blue wavelength lights are emitted in turn.

However, when optical paths of the red, green and blue wavelength lightsare made to be one and the same in such a case, the blue wavelengthsource light is reflected and mixed with the red or green wavelengthfluorescent light which emits when the red or green fluorescentsubstance layer is irradiated with the blue excitation light. Therefore,there may be a problem that color purities deteriorate.

In addition, since the incidence surface and the emission surface of theblue wavelength light in the fluorescent wheel are one and the same,there is a problem that special configuration of an optical layout or anoptical component is required for separating an optical path forincidence of the blue source light from an optical path for emission ofthe blue source light.

SUMMARY

The present invention was developed in consideration of such problems inthe background art. One of objects of the invention is to provide alight source device in which a fluorescent wheel itself is formed as areflective plate without providing its fluorescent wheel surface withany special reflective layer for reflecting only light of a specificwavelength band, while a transmissive portion which can transmit sourcelight is provided in a part of the reflective plate so that an emissionlight path of the source light emitted from the fluorescent wheel can beseparated from an emission light path of fluorescent light of eachcolor, so that the light source device can be made simple inconfiguration and easy in manufacturing, while light of each color canbe emitted with high color purity. Another object of the invention is toprovide a projector including the light source device.

A light source device according to the invention includes: a lightemitting plate that has a plurality of segment regions in a substrate,at least one of the segment regions being formed as a reflectiveportion, a fluorescent substance layer being formed in the reflectiveportion to receive excitation light and emit light of a predeterminedwavelength band in response to the received excitation light, at leastone of the segment regions being formed as a transmissive portion whichcan transmit light; a light source that irradiates the fluorescentsubstance layer of the light emitting plate with the excitation light; adichroic mirror that is disposed between the light source and the lightemitting plate to transmit the excitation light and reflect fluorescentlight from fluorescent substances of the fluorescent substance layer;and a plurality of reflective mirrors or dichroic mirrors that cancondense, on one and the same optical path, the excitation lighttransmitted by the transmissive portion of the light emitting plate andthe fluorescent light reflected by the dichroic mirror, and can radiatethe condensed lights in one and the same direction.

BRIEF DESCRIPTION OF THE DRAWINGS

A general configuration that implements the various feature of theinvention will be described with reference to the drawings. The drawingsand the associated descriptions are provided to illustrate embodimentsof the invention and not to limit the scope of the invention.

FIG. 1 is an external perspective view showing a projector including alight source device according to an embodiment of the invention.

FIG. 2 is a diagram showing functional circuit blocks of the projectorincluding the light source device according to the embodiment of theinvention.

FIG. 3 is a schematic plan view showing an internal configuration of theprojector including the light source device according to the embodimentof the invention.

FIGS. 4A and 4B are a front view and a partially sectional viewschematically showing a fluorescent wheel according to the embodiment ofthe invention.

FIG. 5 is a schematic plan view showing the light source deviceaccording to the embodiment of the invention;

FIGS. 6A-6G are schematic views showing variations of optical paths ofsource light and fluorescent light in the light source device accordingto the embodiment of the invention.

FIG. 7 is a table showing examples of combinations of optical axisconverting mirrors in the light source device according to theembodiment of the invention.

DETAILED DESCRIPTION

An embodiment according to the present invention will be described indetail with reference to the accompanying drawings. The scope of theclaimed invention should not be limited to the examples illustrated inthe drawings and those described below.

In the following description, a projector 10 will be described as anembodiment of the present invention. The projector 10 is provided with alight source device 63, a display element 51, a cooling fan, asource-side optical system 62, a projection-side optical system 90, anda projector control unit. The source-side optical system 62 guides lightfrom the light source device 63 to the display element 51. Theprojection-side optical system 90 projects an image emitted from thedisplay element 51 onto a screen. The projector control unit controlsthe light source device 63 and the display element 51.

The light source device 63 has a fluorescent wheel 71 which is a lightemitting plate. The fluorescent wheel 71 has three fan-shaped segmentregions in a substrate which can be controllably rotated. The segmentregions are adjacent to one another. Of the three, two segment regionsare formed as reflective portions, in which fluorescent substance layers131G and 131R are formed respectively. The fluorescent substance layer131G emits green wavelength light in response to excitation light. Thefluorescent substance layer 131R emits red wavelength light likewise.The remaining segment region is formed as a transmissive portion, whichtransmits light.

Specifically, the transmissive portion which can transmit excitationlight and the reflective portions are disposed circumferentially, and aplurality of fluorescent substance layers 131 for emitting light indifferent wavelength bands are formed circumferentially in thereflective portions. The light source device 63 further has a wheelmotor 73, a light source 72, a first optical axis converting mirror 1,and a plurality of reflective mirrors or dichroic mirrors. The wheelmotor 73 is a drive unit for rotating the fluorescent wheel 71. Thelight source 72 irradiates the fluorescent substance layers 131 of thefluorescent wheel 71 with excitation light. The first optical axisconverting mirror 1 is a dichroic mirror which is disposed between thelight source 72 and the fluorescent wheel 71 so as to transmit theexcitation light and reflect fluorescent light from the fluorescentsubstances. The reflective mirrors or dichroic mirrors can condense theexcitation light transmitted by the transmissive portion of thefluorescent wheel 71 and the fluorescent light reflected by the firstoptical axis converting mirror 1 on one and the same optical path, andradiate the condensed lights in one and the same direction.

The light source 72 for irradiating the fluorescent wheel 71 with theexcitation light is a laser light emitter which emits blue wavelengthlaser light. The fluorescent substance layers 131 are formed of aplurality of fluorescent substances. The fluorescent substances includea fluorescent substance which emits red wavelength light and afluorescent substance which emits green wavelength light, as describedabove.

A diffusion layer 141 for diffusing the excitation light is formed in adiffusion plate 140 serving as the transmissive portion of thefluorescent wheel 71.

The light source device 63 has a condensing optical system which isformed out of a plurality of lenses and mirrors including the dichroicmirrors or the like. The lenses are disposed between the light source 72and the fluorescent wheel 71 and on a path of the fluorescent lightemitted from the fluorescent wheel 71 or the source light transmitted bythe fluorescent wheel 71 so as to condense the lights in cooperationwith the mirrors.

The condensing optical system has first to fourth optical axisconverting mirrors 1 to 4. The first optical axis converting mirror 1 isa dichroic mirror disposed between the fluorescent wheel 71 and thelight source 72 so as to transmit the source light emitted from thelight source 72 without changing the optical axis of the source light,and convert the direction of the optical axis of the fluorescent lightemitted from each fluorescent substance layer 131. The second opticalaxis converting mirror 2 is a normal reflective mirror for convertingthe direction of the optical axis of the source light transmitted by thediffusion layer 141 of the fluorescent wheel 71. The third optical axisconverting mirror 3 further converts the optical axis of the fluorescentlight converted by the first optical axis converting mirror 1. Thefourth optical axis converting mirror 4 transmits the source lightconverted by the second optical axis converting mirror 2 withoutconverting the optical axis of the source light and further converts theoptical axis of the fluorescent light converted by the third opticalaxis converting mirror 3 so as to condense the fluorescent light and thesource light on one and the same optical path.

Specifically, the first optical axis converting mirror 1 is disposed onthe optical axis of the light source 72 and between the fluorescentwheel 71 and the light source 72. The second optical axis convertingmirror 2 is disposed on the optical axis of the light source 72 and inan opposite position to the light source 72 with respect to thefluorescent wheel 71. The third optical axis converting mirror 3 isdisposed on the optical axis of the fluorescent light converted by thefirst optical axis converting mirror 1. The fourth optical axisconverting mirror 4 is disposed in opposition to the second and thirdoptical axis converting mirrors 2 and 3.

The second to fourth optical axis converting mirrors 2 to 4 are composedof two reflective mirrors and one dichroic mirror. The reflectivemirrors convert the optical axis of the source light or the fluorescentlight. The dichroic mirror transmits the source light without convertingthe optical axis of the source light, and converts the axis of thefluorescent light.

The second optical axis converting mirror 2 is formed as a reflectivemirror that converts by 90 degrees the optical axis of the source lighttransmitted by the diffusion layer 141 of the fluorescent wheel 71. Thethird optical axis converting mirror 3 is formed as a reflective mirrorthat converts by 90 degrees the optical axis of the fluorescent lightconverted by the first optical axis converting mirror 1. The fourthoptical axis converting mirror 4 is formed as a dichroic mirror thatconverts by 90 degrees the optical axis of the fluorescent lightconverted by the third optical axis converting mirror 3 without changingthe optical axis of the source light converted by the second opticalaxis converting mirror 2.

FIG. 1 is an external perspective view of the projector 10. In thisembodiment, left and right will designate the left and right directionswith respect to a projection direction, and front and rear willdesignate the front and rear directions with respect to a travellingdirection of a pencil of rays emitted from the projector 10. As shown inFIG. 1, the projector 10 has a substantially rectangular boxed shape, inwhich a lens cover 19 for covering a projection opening is providedlaterally next to a front panel 12 serving as a front side plate of abody casing, and a plurality of exhaust holes 17 are provided in thefront panel 12. Further, an IR receiver for receiving a control signalfrom a not-shown remote controller is provided.

In addition, a user interface 37 is provided in a top panel 11 thatserves as the body casing. Keys and indicators such as a powerindicator, a projection switch key and an overheat indicator aredisposed in the user interface 37. The power indicator informs a user ofon/off of a power switch key or a power supply. The projection switchkey switches on/off projection. The overheat indicator informs the userof overheat of the light source device, the display element, the controlcircuit or the like.

Further, various terminals 20 of an input/output connector, a powersupply adaptor plug, etc. are provided on the back face of the bodycasing. In the input/output connector, USB terminals, a D-SUB terminalfor image signal input, an S terminal, an RCA terminal, etc. areprovided in a back panel. A plurality of intakes 18 are formed near thelower portions of a not-shown right panel 14 and a left panel 15 shownin FIG. 1. The panels 14 and 15 are side plates of the body casing.

Next, a projector control unit of the projector 10 will be describedwith reference to the block diagram of FIG. 2. The projector controlunit is configured by a controller 38, an input/output interface 22, animage converter 23, a display encoder 24 and a display driver 26. Imagesignals conforming to various standards and inputted from aninput/output connector 21 are output through the input/output interface22 and a system bus (SB) to the image converter 23. In the imageconverter 23, the image signals are converted into image signals of apredetermined unified format suitable to be displayed, and outputted tothe display encoder 24.

The display encoder 24 expands and stores the inputted image signals ina video RAM 25, then generates video signals from the stored contents ofthe video RAM 25 and outputs the video signals to the display driver 26.

The display driver 26 drives the display element 51, which is a spatialoptical modulator (SOM), at a proper frame rate in accordance with theimage signals outputted from the display encoder 24. When the lightsource 72 of the light source device 63 is turned on, a pencil of raysemitted from the light source device 63 is made incident on the displayelement 51 through the source-side optical system so that an opticalimage is formed out of light reflected by the display element 51controlled by the display driver 26. Thus, an image can be projected anddisplayed on a not-shown screen through a projection-system lens groupserving as the projection-side optical system. A movable lens group 97of the projection-side optical system is driven for zoom adjustment andfocus adjustment by a lens motor 45.

An image processor 31 performs a recording process in which data of aluminance signal and a color-difference signal of an image signal arecompressed by processing such as ADCT and Huffman encoding andsequentially written into a memory card 32 which is a removablerecording medium. Further, in a reproduction mode, the image processor31 performs a process in which image data recorded on the memory card 32is read out, and individual image data forming a series of moving imagesis expanded frame by frame and outputted to the display encoder 24through the image converter 23 so that the moving images or the like canbe displayed based on the image data stored in the memory card 32.

The controller 38 manages operation control of each circuit in theprojector 10. The controller 38 is configured by a CPU, a ROM fixedlystoring operating programs such as various settings, a RAM used as awork memory, etc.

An operation signal of the user interface 37 configured by main keys,indicators, etc. provided in the top panel 11 of the body casing is setout directly to the controller 38. A key operation signal from theremote controller is received by an IR receiver 35, and a code signaldemodulated by an IR processor 36 is outputted to the controller 38.

An audio processor 47 is connected to the controller 38 through thesystem bus (SB). The audio processor 47 has a sound source circuit of aPCM sound source or the like. In a projection mode and a reproductionmode, the audio processor 47 converts audio data into analog data, anddrives a speaker 48 to reinforce and release sound.

In addition, the controller 38 controls a power supply control circuit41. When the power switch key is operated, the power supply controlcircuit 41 turns on the light source 72 of the light source device 63.Further, the controller 38 controls a cooling fan drive control circuit43 to perform temperature detection using a plurality of temperaturesensors provided in the light source device 63 and so on, and controlthe rotational velocity of the cooling fan based on the result of thetemperature detection. In addition, the controller 38 controls thecooling fan drive control circuit 43 to keep on rotating the cooling fanby use of a timer or the like even after the projector body is poweredoff. Further, in accordance with the result of the temperature detectionusing the temperature sensors, the controller 38 controls variouscomponents provided in the projector 10 to be powered off.

Next, the internal configuration of the projector 10 will be described.FIG. 3 is a schematic plan view showing the internal configuration ofthe projector 10. In the projector 10, as shown in FIG. 3, a powersupply control circuit board 102 to which a power supply circuit block101 etc. are attached is disposed near the right panel 14, a sirocco fantype blower 110 is disposed substantially in the center, a controlcircuit board 103 is disposed near the blower 110, the light sourcedevice 63 is disposed near the front panel 12, and an optical systemunit 70 is disposed near the left panel 15. In addition, the spaceinside the housing of the projector 10 is air-tightly sectioned into anintake-side spatial chamber 121 on the back panel 13 side and anexhaust-side spatial chamber 122 on the front panel 12 side by asectioning partition 120. The blower 110 is disposed so that an inletport 111 is located in the intake-side spatial chamber 121 and an outletport 113 is located in the border between the exhaust-side spatialchamber 122 and the intake-side spatial chamber 121.

The optical system unit 70 has a substantially U-shape, which isconfigured by three blocks, that is, a lighting-side block 78 locatednear the light source device 63, an image generation block 79 located onthe back panel 13 side, and a projection-side block 80 located betweenthe lighting-side block 78 and the left panel 15.

The lighting-side block 78 has a part of the source-side optical system62 by which light emitted from the light source device 63 is guided tothe display element 51 belonging to the image generation block 79. Thesource-side optical system 62 belonging to the lighting-side block 78includes a light guide device 75 by which a pencil of rays emitted fromthe light source device 63 can be formed into a luminous flux with auniform intensity distribution, a condenser lens which can condenselight transmitted by the light guide device 75, etc.

The image generation block 79 has an optical axis changing mirror 74, aplurality of condenser lenses and an irradiation mirror 84 as thesource-side optical system 62. The optical axis changing mirror 74changes the direction of the optical axis of the pencil of rays emittedfrom the light guide device 75. Light reflected by the optical axischanging mirror 74 is condensed on the display element 51 by thecondenser lenses. By the irradiation mirror 84, the pencil of raystransmitted by the condenser lenses is radiated on the display element51 at a predetermined angle. Further, the image generating block 79 hasa DMD formed as the display element 51. A display element cooling unit53 for cooling the display element 51 is disposed on the back panel 13side of the display element 51 so as to prevent the display element 51from reaching a high temperature.

The projection-side block 80 has a lens group of the projection-sideoptical system 90 for releasing light which is reflected by the displayelement 51 and forms an image onto a screen. The projection-side opticalsystem 90 is a varifocal lens system with a zoom function, whichincludes a fixed lens group 93 built in a fixed lens-barrel and amovable lens group 97 built in a movable lens-barrel. The movable lensgroup 97 can be moved for zoom adjustment or focus adjustment by a lensmotor.

In addition, in the internal configuration of the projector 10, membersto be lower in temperature than the light source device 63 are disposedin the intake-side spatial chamber 121. Specifically, the power supplycontrol circuit board 102, the blower 110, the control circuit board103, the image generation block 79 of the optical system unit 70, theprojection-side block 80 of the optical system unit 70, and thecondenser lenses in the lighting-side block 78 of the optical systemunit 70 are disposed in the intake-side spatial chamber 121.

On the other hand, the light source device 63 which may reach acomparatively high temperature, the light guide device 75 belonging tothe lighting-side block 78 of the optical system unit 70, and an exhausttemperature reduction unit 114 are disposed in the exhaust-side spatialchamber 122.

The light source device 63 has a fluorescent wheel 71, a wheel motor 73,a plurality of light sources 72, and a plurality of mirrors. Thefluorescent wheel 71 is a light emitting plate which is irradiated withlight to thereby emit lights in wavelength bands of red, green and blue,which are the light's three primary colors. The wheel motor 73 is adrive unit for driving and rotating the fluorescent wheel 71. By thelight sources 72, the fluorescent wheel 71 is irradiated with bluewavelength light. The mirrors guide the red, green and blue wavelengthlights emitted from the fluorescent wheel 71 to the light guide device75.

The light sources 72 are disposed so that the optical axis of each lightsource 72 can cross the optical axis of the light guide device 75substantially at right angles. In addition, the fluorescent wheel 71 isdisposed near the front panel 12 so as to face the light sources 72.Specifically, the fluorescent wheel 71 is disposed to set the wheelsurface thereof to cross the optical axis of each light source 72 atright angles. That is, the rotational axis of the wheel motor 73 forrotating the fluorescent wheel 71 is parallel to the optical axis ofeach light source 72. In addition, the fluorescent wheel 71 is designedto emit red and green fluorescent lights toward the light sources 72 andtransmit blue wavelength light from the light sources 72.

The fluorescent wheel 71 serving as a light emitting plate has threefan-shaped segment regions in a disc-like substrate as shown in FIG. 4A.Of the three, two segment regions are formed as reflective portions, andthe remaining segment region is formed as a transmissive portion.Specifically, in the fluorescent wheel 71, a reflective plate 130 and adiffusion plate 140 are fixedly bonded to a motor hub so as to be formedintegrally. In the reflective plate 130 serving as fan-shaped reflectiveportions, a red fluorescent substance layer 131R and a green fluorescentsubstance layer 131G are disposed circumferentially adjacently to eachother as layers 131 of two kinds of fluorescent substances for emittinglights of different wavelength bands respectively. In the diffusionplate 140 serving as a fan-shaped transmissive portion, a diffusionlayer 141 is disposed adjacently to the fluorescent substance layers131. The motor hub is provided on a rotation shaft of the wheel motor73. In addition, the reflective plate 130 and the diffusion plate 140are bonded to each other on their boundary surfaces.

A circular opening corresponding to the shape of a columnar rotationshaft which is a connection portion of the fluorescent wheel 71 with thewheel motor 73 is formed in the central portion of the fluorescent wheel71. The rotation shaft is inserted into the circular opening, and themotor hub is bonded to the reflective plate 130 and the diffusion plate140 near their central portions so as to be firmly connected thereto.

Thus, the fluorescent wheel 71 rotates circumferentially and integrally,for example, at a rotational velocity of about 120 rps, by the wheelmotor 73 serving as a drive unit which is driven and controlled by thecontroller 38 serving as a projector control unit.

The reflective plate 130 serving as the reflective portions consists ofan opaque substrate made from a thermal conductive member such as acopper plate or an aluminum plate. By silver deposition or the like, areflective layer for reflecting blue source light from the light source72 and red and green wavelength fluorescent lights generated by thefluorescent substances is formed all over the light source 72 sidesurface of the reflective plate 130 to which the fluorescent substancelayers 131 will be attached. The fluorescent substance layers 131 areformed on the reflective layer. The reflective layer can be formedeasily by mirror finishing one surface of the reflective plate 130.

The two kinds of belt-like fluorescent substance layers 131 are formedby coating so as to be disposed circumferentially adjacently to eachother near the outer circumferential portion of the reflective plate 130which has a fan-like shape with a major arc wider than a semicircle. Ared fluorescent substance layer 131R containing a fluorescent substanceis formed on the reflective plate 130. When the fluorescent substance isirradiated with the source light, the fluorescent substance absorbs thelight from the light sources 72 as excitation light. Thus, the excitedfluorescent substance emits red wavelength light which is one of theprimary colors. In the same manner, a green fluorescent substance layer131G containing a fluorescent substance is formed adjacently to the redfluorescent substance layer 131R. When the fluorescent substance isirradiated with the source light, the fluorescent substance absorbs thelight from the light sources 72 as excitation light. Thus, the excitedfluorescent substance emits green wavelength light which is one of theprimary colors. Each fluorescent substance layer 131 consists offluorescent crystals and binder.

The diffusion plate 140 serving as the transmissive portion consists ofa transparent substrate such as a glass substrate or a transparent resinsubstrate. The diffusion plate 140 has a diffusion layer 141 all overthe light source 72 side surface. Specifically, in the diffusion plate140, the whole of one surface of the transparent substrate having a fanshape with a minor arc about ⅓ as long as the circumference is subjectedto optical treatment such as surface texturing by blasting or the like.Thus, the diffusion layer 141 is formed to provide a diffusion effect toincident blue source light which transmits the diffusion plate 140.

The diffusion plate 140 is disposed so as to be circumferentiallyadjacent to the reflective plate 130. Thus, the diffusion layer 141 isdisposed adjacently to the fluorescent substance layers 131. Thediffusion layer 141 may be formed by fixedly attaching a belt-like solidoptical material as well as by applying the optical treatment to thesurface of the transparent substrate. In addition, the diffusion layer141 may be formed not on the light source 72 side but on the oppositesurface thereto.

A laser light emitter or a blue light emitting diode which can radiatelight to the fluorescent substance layers 131 and the diffusion layer141 disposed near the outer circumferential portion of the fluorescentwheel 71 is used as each light source 72. The laser light emitter orblue light emitting diode can emit blue wavelength light which is avisible light with a shorter wavelength than any of the red and greenwavelength lights emitted from the red and green fluorescent substancelayers 131R and 131G.

In this manner, the light sources 72 and the fluorescent wheel 71 havingthe fluorescent substance layers 131 and the diffusion layer 141 aredisposed oppositely to each other. Thus, the fluorescent light emittedfrom each of the fluorescent substance layers 131 formed in thereflective portions of the fluorescent wheel 71 can be separated fromthe source light transmitted by the diffusion plate 140 serving as thetransmissive portion of the fluorescent wheel 71. That is, thefluorescent substance layers 131 and the diffusion layer 141 of thefluorescent wheel 71 which is rotating are irradiated with blue sourcelight sequentially. Thus, fluorescent light is emitted toward the sideof the light sources 72 when any fluorescent substance layer 131 of thefluorescent wheel 71 is irradiated with the source light emitted fromthe light sources 72 as excitation light. When the diffusion layer 141of the transmissive portion of the fluorescent wheel 71 is irradiatedwith the source light emitted from the light sources 72, the sourcelight is diffused and transmitted oppositely to the light sources 72.

The reflective layer is formed on the surface where the fluorescentsubstance layers 131 are disposed in the reflective plate 130 serving asthe reflective portions. When the red fluorescent substance layer 131Ris irradiated with directional source light from the light sources 72,the fluorescent substance of the red fluorescent substance layer 131Rabsorbs the blue light as excitation light and emits red wavelengthfluorescent light omnidirectionally. Part of the red fluorescent lightemitted toward the light sources 72 is incident on the light guidedevice 75 through the condensing optical system having mirrors. Redfluorescent light emitted toward the opaque substrate is reflected bythe reflective layer. Most of the reflected light is incident on thelight guide device 75 through the condensing optical system having themirrors, as light emitted from the fluorescent wheel 71.

The blue source light radiated to the reflective layer without beingabsorbed by the fluorescent substance of the red fluorescent substancelayer 131R can be reflected by the reflective layer and emitted againtoward the red fluorescent substance layer 131R so as to excite thefluorescent substance. Therefore, efficiency of using the blue sourcelight can be improved and light emission can be made bright.

On the other hand, blue source light reflected by the reflective layerand returning from the red fluorescent substance layer 131R toward thelight sources 72 without being absorbed by the fluorescent substancetravels from the red fluorescent substance layer 131R toward the lightsources 72 together with the red fluorescent light. However, the bluesource light is separated from the red fluorescent light by a dichroicmirror serving as an optical axis converting mirror which can reflectred light and transmit blue light. That is, of the light emitted fromthe fluorescent wheel 71 toward the light sources 72, only the redfluorescent light is reflected by the dichroic mirror and incident onthe light guide device 75 through other mirrors or lenses of thecondensing optical system.

In the same manner, when the green fluorescent substance layer 131G isirradiated with light from the light sources 72, green wavelengthfluorescent light is emitted from the green fluorescent substance asbrightly as the red fluorescent light. The green fluorescent light isseparated from blue source light reflected by the optical axisconverting mirror and returning toward the light sources 72, and thenincident on the light guide device 75 through other mirrors or lenses ofthe condensing optical system.

When the diffusion layer 141 is irradiated with source light such asblue wavelength laser light from the light sources 72, the diffusionlayer 141 provides a diffusion effect to the blue source light incidentthereon. Thus, blue light formed as diffused light in the same manner asthe lights (red light and green light) emitted from the fluorescentsubstance layers 131 is emitted from the diffusion layer 141. The bluelight is incident on the light guide device 75 through the condensingoptical system having the mirrors.

As a result, when directional source light is emitted from the lightsources 72 while the fluorescent wheel 71 is rotated, red, green andblue wavelength lights are sequentially incident on the light guidedevice 75 from the fluorescent wheel 71 through the condensing opticalsystem having the mirrors. The DMD which is the display element 51 ofthe projector 10 displays light of each color in accordance with data bytime division. Thus, a color image can be generated on a screen.

As shown in FIG. 5, the light source device 63 has collimator lenses 150disposed on the optical axes of the light sources 72 and on theiremitting side respectively. By the collimator lenses 150, light emittedfrom the light sources 72 is converted into parallel beams. The lightsource device 63 has a condensing optical system configured by first tofourth optical axis converting mirrors 1 to 4, a plurality of convexlenses, etc. Each optical axis converting mirror 1-4 reflects ortransmits light of a predetermined wavelength band emitted from thefluorescent wheel 71 so as to condense the light of each color emittedfrom the fluorescent wheel 71 onto one and the same optical path. Theconvex lenses condense pencils of rays emitted from the fluorescentwheel 71 and incident on the light guide device 75.

The condensing optical system according to this embodiment will bedescribed below. The condensing optical system has four optical axisconverting mirrors which are disposed in predetermined positions so thatthe optical axis of red/green fluorescent light and the optical axis ofblue source light emitted and separated in different directions from thefluorescent wheel 71 can be brought into line with each other, and thered/green light and the blue light can be condensed on one and the sameoptical path. The optical axis converting mirrors consist of a dichroicmirror which is disposed between the light sources 72 and thefluorescent wheel 71 so as to transmit excitation light and reflectfluorescent light from the fluorescent substances, and a plurality ofreflective mirrors or dichroic mirrors which can condense the excitationlight transmitted by the transmissive portion of the fluorescent wheel71 and the fluorescent light reflected by the dichroic mirror on one andthe same optical path and radiate the condensed lights in one and thesame direction.

Specifically, the condensing optical system has first to fourth opticalaxis converting mirrors 1 to 4. The first optical axis converting mirror1 is a dichroic mirror which is disposed between the fluorescent wheel71 and the light sources 72 so as to transmit source light emitted fromthe light sources 72 without changing the optical axis of the sourcelight and convert the direction of the optical axis of the fluorescentlight emitted from each fluorescent substance layer 131. The secondoptical axis converting mirror 2 converts the direction of the opticalaxis of the source light transmitted by the diffusion layer 141 of thefluorescent wheel 71. The third and fourth optical axis convertingmirrors 3 and 4 further convert the optical axis of the fluorescentlight converted by the first optical axis converting mirror 1 and theoptical axis converted by the second optical axis converting mirror 2 soas to bring the optical axis of the fluorescent light and the opticalaxis of the source light into line with each other and condense thefluorescent light and the source light on one and the same optical path.

According to this embodiment, the first optical axis converting mirror 1is a dichroic mirror which is disposed on the optical axes of the lightsources 72 and between the light sources 72 and the fluorescent wheel 71so as not to change the optical axis of the blue source light emittedfrom the light sources 72 but to convert, by 90 degrees, the directionof the optical axis of the red/green fluorescent light emitted from thefluorescent wheel 71. That is, the first optical axis converting mirror1 transmits the blue source light emitted from the light sources 72 asexcitation light and reflects the red/green wavelength fluorescent lightemitted from the fluorescent substance of each fluorescent substancelayer 131 of the fluorescent wheel 71 while changing the direction ofthe red/green wavelength fluorescent light by the angle of 90 degrees.

The second optical axis converting mirror 2 is a normal reflectivemirror which is disposed on the optical axes of the light sources 72 andon the opposite side to the light sources 72 with respect to thefluorescent wheel 71 so as to convert, by 90 degrees, the optical axisof the blue source light transmitted by the diffusion layer 141 in thetransmissive portion of the fluorescent wheel 71. That is, the secondoptical axis converting mirror 2 reflects the blue wavelength lightemitted from the fluorescent wheel 71 while changing the direction ofthe blue wavelength light by the angle of 90 degrees. The second opticalaxis converting mirror 2 may be formed not as the reflective mirror butas a dichroic mirror which can reflect blue wavelength light.

The third optical axis converting mirror 3 is a reflective mirror whichis disposed to face the first optical axis converting mirror 1 on theoptical axis of the red/green fluorescent light converted by the firstoptical axis converting mirror 1, so as to convert, by 90 degrees, theoptical axis of the fluorescent light converted by the first opticalaxis converting mirror 1. That is, the third optical axis convertingmirror 3 reflects the red/green wavelength fluorescent light reflectedby the first optical axis converting mirror 1 while further changing thedirection of the red/green wavelength fluorescent light by the angle of90 degrees. The third optical axis converting mirror 3 may be formed notas the reflective mirror but as a dichroic mirror which can reflect redand green lights.

The fourth optical axis converting mirror 4 is a dichroic mirror whichis disposed to face the second optical axis converting mirror 2 and thethird optical axis converting mirror 3 so as to convert, by 90 degrees,the optical axis of the red/green fluorescent light converted by thethird optical axis converting mirror 3 without changing the optical axisof the blue source light converted by the second optical axis convertingmirror 2. That is, the fourth optical axis converting mirror 4 isdisposed in a position where the optical axis of the blue source lightreflected by the second optical axis converting mirror 2 crosses theoptical axis of the red/green wavelength fluorescent light reflected bythe third optical axis converting mirror 3, so as to transmit the bluesource light reflected by the second optical axis converting mirror 2and make the transmitted blue source light travel straight, whilereflecting the red/green wavelength fluorescent light to change thedirection of the red/green wavelength fluorescent light reflected by thethird optical axis converting mirror 3 by the angle of 90 degrees.

As a result, the blue source light transmitted by the fourth opticalaxis converting mirror 4 and the red/green fluorescent light reflectedby the fourth optical axis converting mirror 4 can be condensed on oneand the same optical path, and all the lights of the colors can beemitted in one and the same direction.

In this manner, the four optical axis converting mirrors 1 to 4 aredisposed in the condensing optical system so as to convert the opticalaxis of each color light emitted from the fluorescent wheel 71 and bringthe optical axis of the color light into line with the optical axis ofthe light guide device 75. Thus, all the lights of the colors can becondensed on one and the same optical path and radiated in one and thesame direction so that all the lights of the colors emitted from thefluorescent wheel 71 can be made incident on the light guide device 75sequentially.

The condensing optical system is formed out of a plurality of lenses andmirrors such as dichroic mirrors. The lenses are disposed between thelight sources 72 and the fluorescent wheel 71 and on the path of thefluorescent light from the fluorescent wheel 71 or the source lighttransmitted by the fluorescent wheel 71 so as to condense the lights incooperation with the mirrors. Thus, pencils of rays whose travellingdirections have been changed by the mirrors are condensed by the lensesso that the lights can be made incident on the light guide device 75efficiently.

Specifically, when the light sources 72 are blue light emitting diodes,blue lights emitted from the light sources 72 are formed into parallellights by the collimator lenses 150 respectively. Alternatively, whenthe light sources 72 are blue laser light emitters, blue lights areformed into parallel lights with increased directivity by the collimatorlenses 150 respectively. The parallel lights are condensed by a firstconvex lens 153 a disposed between the collimator lenses 150 and thefirst optical axis converting mirror 1. In addition, due to a condenserlens group 155 disposed near the front and back sides of the fluorescentwheel 71 respectively, blue wavelength light condensed by the firstconvex lens 153 a is further condensed by the condenser lens group 155,and the fluorescent wheel 71 is irradiated with the condensed light. Atthe same time, pencils of rays emitted from the front and back sides ofthe fluorescent wheel 71 are also condensed.

Further, a second convex lens 153 b is disposed between the secondoptical axis converting mirror 2 and the fourth optical axis convertingmirror 4. A third convex lens 153 c is disposed between the firstoptical axis converting mirror 1 and the third optical axis convertingmirror 3. A fourth convex lens 153 d is disposed between the thirdoptical axis converting mirror 3 and the fourth optical axis convertingmirror 4. Further, a light guide device entrance lens 154 is disposedbetween the fourth optical axis converting mirror 4 and the light guidedevice 75. Thus, light emitted from the fluorescent wheel 71 is formedinto a condensed pencil of rays, which is incident on the light guidedevice 75.

Thus, the blue source light emitted from the light sources 72 throughthe collimator lenses 150 is condensed by the first convex lens 153 a,transmitted by the first optical axis converting mirror 1, furthercondensed by the condenser lens group 155, and radiated to thefluorescent substance layers 131 or the diffusion layer 141 of thefluorescent wheel 71.

Then, when the diffusion layer 141 of the diffusion plate 140 serving asthe transmissive portion of the fluorescent wheel 71 is irradiated withthe source light, blue source light transmitted by the diffusion layer141 is formed into diffused light, and condensed by the condenser lensgroup 155 disposed on the opposite side of the fluorescent wheel 71 tothe light sources 72. Then, the second optical axis converting mirror 2is irradiated with the condensed blue source light. In addition, theblue source light is reflected by the second optical axis convertingmirror 2 and then condensed by the second convex lens 153 b. After that,the condensed blue source light is transmitted by the fourth opticalaxis converting mirror 4 and condensed by the light guide deviceentrance lens 154. Thus, the condensed blue source light is incident onthe light guide device 75.

When any of the fluorescent substance layers 131 of the reflective plate130 serving as the reflective portions of the fluorescent wheel 71 isirradiated with the source light, red or green wavelength fluorescentlight is emitted toward the source lights 72. The fluorescent light iscondensed by the condenser lens group 155 on the light source 72 side ofthe fluorescent wheel 71, and radiated to the first optical axisconverting mirror 1. Here, the fluorescent light is reflected by thefirst optical axis converting mirror 1. However, the blue source lightreflected without being absorbed by the fluorescent substance of thefluorescent substance layer 131 is transmitted by the first optical axisconverting mirror 1. Thus, the red or green fluorescent light and theblue source light are separated so that their color purities can beprevented from deteriorating.

In addition, the fluorescent light reflected by the first optical axisconverting mirror 1 is condensed by the third convex lens 153 c, andradiated to the third optical axis converting mirror 3. The fluorescentlight is reflected by the third optical axis converting mirror 3, andcondensed by the fourth convex lens 153 d. After that, the fluorescentlight is radiated to the fourth optical axis converting mirror 4. Thefluorescent light is further reflected by the fourth optical axisconverting mirror 4 and condensed by the light guide device entrancelens 154. Thus, the fluorescent light is incident on the light guidedevice 75.

In this manner, according to the invention, a special reflective layerfor reflecting only specific wavelength light is not provided on thesurface of the fluorescent wheel 71, but the fluorescent wheel 71 itselfis formed as the reflective plate 130 and the diffusion plate 140including the diffusion layer 141 for transmitting source light anddiffusing the source light is provided as a transmissive portion in apart of the reflective plate 130. Thus, the emission optical paths ofthe source light and the fluorescent light of each color emitted fromthe fluorescent wheel 71 can be separated. It is therefore possible toprovide the light source device 63 which is simple in configuration andeasy in manufacturing, and the projector 10 having the light sourcedevice 63.

The light emitted from the fluorescent wheel 71 includes not only red orgreen fluorescent light but also a slight volume of blue source lightreflected by the fluorescent wheel 71. However, since the first opticalaxis converting mirror 1 formed as a dichroic mirror is disposed betweenthe light sources 72 and the fluorescent wheel 71, the blue source lightreflected by the fluorescent wheel 71 and mixed with the red or greenwavelength fluorescent light can be cut. It is therefore possible toprovide the light source device 63 in which the source light can besurely prevented from being mixed with the fluorescent light and eachcolor light can be emitted with high color purity, and the projector 10having the light source device 63.

When blue wavelength laser light emitters are used as the light sources72, each fluorescent substance can be excited to generate lightefficiently. In addition, when the fluorescent substance layers 131containing at least a fluorescent substance for emitting red wavelengthlight and a fluorescent substance for emitting green wavelength lightare formed in the fluorescent wheel 71, it is possible to generatelights of red and green wavelength bands belonging to the primarycolors. Further, when the diffusion layer 141 is provided in thetransmissive portion, directional laser light can be diffused andtransmitted so that light of a blue wavelength band belonging to theprimary colors can be made incident on the light guide device 75 asdiffused light similar to the fluorescent light.

Incidentally, the transmissive portion may be formed out of a normalglass plate or a space as a through hole with a frame formedcircumferentially, without providing the diffusion layer 141 in thetransmissive portion. In this case, a diffusion plate is fixedlydisposed on an optical path of blue source light, for example, on thelight source 72 side just close to the fluorescent wheel 71 or betweenthe fluorescent wheel 71 and the second optical axis converting mirror2. Further, when blue light emitting diodes are used as the lightsources 72, the light source device 63 may be configured so that thediffusion layer 141 is not provided on the transmissive portion or onthe optical path of the blue source light.

Various configurations can be used as the kinds and layout of theoptical axis converting mirrors 1 to 4 for use in the condensing opticalsystem of the light source device 63.

Embodiments about other variations of the layout of the optical axisconverting mirrors 1 to 4 will be described below with reference toFIGS. 6A-6G and FIG. 7.

FIG. 6A is a schematic view showing an optical path L of source lightemitted from the light source 72 and an optical path F of fluorescentlight emitted in response to the source light in the optical layout (seeFIG. 5) of the aforementioned light source device 63. That is, in afirst optical layout shown in FIG. 6A, the first optical axis convertingmirror 1 is formed as a dichroic mirror which can transmit blue sourcelight and reflect red and green fluorescent lights as shown in FIG. 7.The second optical axis converting mirror 2 is a reflective mirror whichcan reflect the blue source light. The third optical axis convertingmirror 3 is a reflective mirror which can reflect the red and greenfluorescent lights. The fourth optical axis converting mirror 4 is adichroic mirror which can transmit the blue source light and reflect thered and green fluorescent lights.

The optical layout may be modified into a second optical layout (seeFIG. 6B) in which the fourth optical axis converting mirror 4 in thefirst optical layout is formed as a dichroic mirror which can reflectthe blue source light and transmit the red and green fluorescent lightsas shown in FIG. 7.

Further, a third optical layout (see FIG. 6C) may be used. In the thirdoptical layout, the second optical axis converting mirror 2 is formed asa dichroic mirror which can transmit the blue source light and reflectthe red and green fluorescent lights, and the fourth optical axisconverting mirror 4 is formed as a reflective mirror. In this manner,only the fluorescent lights are reflected repeatedly so that the sourcelight and each fluorescent light can be condensed on one and the sameoptical path on the optical axis of the light source 72.

Another optical layout, that is, a fourth optical layout (see FIG. 6D)may be arranged. In the fourth optical layout, the second optical axisconverting mirror 2 in the third optical layout is formed as a dichroicmirror which can reflect the blue source light and transmit the red andgreen fluorescent lights.

Further, a fifth optical layout (see FIG. 6E) may be used as thecondensing optical system of the light source device 63. In the fifthoptical layout, the second optical axis converting mirror 2 is formed asa reflective mirror which can convert, by 90 degrees, the optical axisof the blue source light transmitted by the diffusion layer 141 of thediffusion plate 140 of the fluorescent wheel 71, the fourth optical axisconverting mirror 4 is formed as a reflective mirror which can convert,by 90 degrees, the optical axis of the blue source light converted bythe second optical axis converting mirror 2, and the third optical axisconverting mirror 3 is formed as a dichroic mirror which does not changethe optical axes of the red and green fluorescent lights converted bythe first optical axis converting mirror 1 but can converts, by 90degrees, the optical axis of the blue source light converted by thefourth optical axis converting mirror 4.

In addition, another optical layout, that is, a sixth optical layout(see FIG. 6F) may be arranged. In the sixth optical layout, the thirdoptical axis converting mirror 3 in the fifth optical layout is formedas a dichroic mirror which can transmit the blue source light andreflect the red and green fluorescent lights.

Moreover, a seventh optical layout (see FIG. 6G) may be used. Theoptical layout is not limited to the aforementioned layout in which thesecond to fourth optical axis converting mirrors 2 to 4 consist of tworeflective mirrors each converting the optical axis of the source lightor the fluorescent light and one dichroic mirror for converting one ofthe optical axes of the source light and the fluorescent light withoutconverting the other, as described above (see FIGS. 6A-6F). In theseventh optical layout, the second to fourth optical axis convertingmirrors 2 to 4 consist of three reflective mirrors for converting theoptical axis of the blue source light. In this optical layout, the bluesource light is chiefly reflected repeatedly so that the blue sourcelight can be condensed on the same optical path as the red and greenfluorescent lights.

In this manner, various optical layouts can be used when the second tofourth optical axis converting mirrors 2 to 4 are disposed inpredetermined positions and angles while various combinations are madeabout the characteristics of the second to fourth optical axisconverting mirrors 2 to 4. Accordingly, not only is it possible toprovide the light source device 63 and the projector 10 high in colorpurity and easy in manufacturing as described above, but it is alsopossible to enhance the degree of freedom in the layout of an apparatussuch as the projector 10 mounted with the light source device 63.

According to the invention, it is possible to provide a light sourcedevice in which a fluorescent wheel itself is formed as a reflectiveplate without providing its fluorescent wheel surface with any specialreflective layer for reflecting only light of a specific wavelengthband, while a transmissive portion which can transmit source light isprovided in a part of the reflective plate so that an emission path ofthe source light emitted from the fluorescent wheel can be separatedfrom an emission path of fluorescent light of each color, so that thelight source device can be made simple in configuration and easy inmanufacturing, while light of each color can be emitted with high colorpurity. It is also possible to provide a projector including the lightsource device.

The invention is not limited to the aforementioned embodiments, but maybe changed or modified desirably without departing from the gist of theinvention. For example, the fluorescent substance layers 131 disposed inthe reflective plate 130 are not limited to the case where the red andgreen fluorescent substance layers 131R and 131G are disposed, but thefluorescent substance layers 131R and 131G may be disposed together withanother fluorescent substance layer which can emit light of a wavelengthband of a complementary color such as yellow.

The number of the optical axis converting mirrors disposed in the lightsource device 63 is not limited to four, but five or more optical axisconverting mirrors may be disposed so that source light and fluorescentlight separated from each other can be condensed on one and the sameoptical path. Preferably, when the four optical axis converting mirrors1 to 4 are provided, the light source device 63 can be made simple andcompact.

In the aforementioned embodiments, dichroic mirrors are used forconverting the directions of optical axes or selecting transmission orreflection of light in accordance with wavelength thereof. However, theinvention is not limited thereto, but the dichroic mirrors may bereplaced by other alternative means such as dichroic prisms.

Further, the fluorescent wheel 71 may be formed not into a disc-likeshape but as a rectangular light emitting plate, and fixedly disposed.In this case, an adjustment unit is disposed between the light sources72 and the light emitting plate so as to change the direction ofirradiation with light from each light source 72. Alternatively, alightsource drive unit for driving to change the position of each lightsource 72 and/or the direction of irradiation therewith may be providedso that a spot irradiated with light from the light source 72 can beplaced in segment regions in turn. Thus, light of each color can be madeincident on the light guide device 75 through a condensing opticalsystem. As the adjustment unit, it is, for example, possible to use anoptical deflector employing various devices, such as a KTN crystal, anacoustooptic element and a MEMS mirror.

It is to be understood that the present invention is not limited to thespecific embodiments described above and that the invention can beembodied with the components modified without departing from the spiritand scope of the invention. The invention can be embodied in variousforms according to appropriate combinations of the components disclosedin the embodiments described above. For example, some components may bedeleted from all components shown in the embodiments. Further, thecomponents in different embodiments may be used appropriately incombination.

1. A light source device comprising: a light emitting plate that has aplurality of segment regions on a substrate, at least one of the segmentregions being formed as a reflective portion on which a fluorescentsubstance layer is formed to receive excitation light and emit light ofa predetermined wavelength band in response to the received excitationlight, and at least one of the segment regions being formed as atransmissive portion that transmits light; a light source thatirradiates the fluorescent substance layer of the light emitting platewith the excitation light; a dichroic mirror that is disposed betweenthe light source and the light emitting plate to transmit the excitationlight and reflect fluorescent light from the fluorescent substancelayer; and an optical device that condenses the excitation lighttransmitted by the transmissive portion of the light emitting plate andthe fluorescent light reflected by the dichroic mirror on a singleoptical path to form a condensed light and radiate the condensed lighttoward the same direction.
 2. The device according to claim 1, whereinthe light source is a blue wavelength laser light emitter.
 3. The deviceaccording to claim 2, wherein the fluorescent substance layer comprisesa first fluorescent substance that emits red wavelength light and asecond fluorescent substance that emits green wavelength light.
 4. Thedevice according to claim 2, wherein the light emitting plate comprisesa diffusion layer formed in the transmissive portion, the diffusionlayer being configured to diffuse the excitation light.
 5. The deviceaccording to claim 1, further comprising: a condensing optical systemthat comprises a plurality of lenses and mirrors comprising the dichroicmirror, the condensing optical system being disposed between the lightsource and the light emitting plate and on a path of the fluorescentlight from the light emitting plate and the excitation light transmittedby the light emitting plate.
 6. The device according to claim 5, whereinthe condensing optical system comprises: a first optical axis convertingmirror that is configured by the dichroic mirror disposed between thelight emitting plate and the light so as to transmit the excitationlight emitted from the light source without changing an optical axis ofthe excitation light, and convert a direction of an optical axis of thefluorescent light emitted from the fluorescent substance layer; a secondoptical axis converting mirror that is configured by one of (1) adichroic mirror or a normal reflective mirror for converting a directionof the optical axis of the excitation light transmitted by thetransmissive portion of the light emitting plate or (2) a dichroicmirror for transmitting the excitation light without converting theoptical axis of the excitation light; a third optical axis convertingmirror; and a fourth optical axis converting mirror.
 7. The deviceaccording to claim 6, wherein the first optical axis converting mirroris disposed on the optical axis of the light source and between thelight emitting plate and the light source, wherein the second opticalaxis converting mirror is disposed on the optical axis of the lightsource and in an opposite position to the light source with respect tothe light emitting plate, wherein the third optical axis convertingmirror is disposed on the optical axis of the fluorescent lightconverted by the first optical axis converting mirror, and wherein thefourth optical axis converting mirror is disposed in opposition to thesecond and third optical axis converting mirrors.
 8. The deviceaccording to claim 6, wherein the second to fourth optical axisconverting mirrors comprise: two reflective mirrors that convert theoptical axis of the excitation light or the fluorescent light; and adichroic mirror that converts one of the axes of the excitation lightand the fluorescent light without converting the other.
 9. The deviceaccording to claim 8, wherein the second optical axis converting mirroris configured by a reflective mirror that converts by 90 degrees theoptical axis of the excitation light transmitted by the transmissiveportion of the light emitting plate, wherein the third optical axisconverting mirror is configured by a reflective mirror that converts by90 degrees the optical axis of the fluorescent light converted by thefirst optical axis converting mirror, and wherein the fourth opticalaxis converting mirror is configured by a dichroic mirror that convertsby 90 degrees the optical axis of the fluorescent light converted by thethird optical axis converting mirror without changing the optical axisof the excitation light converted by the second optical axis convertingmirror.
 10. The device according to claim 8, wherein the second opticalaxis converting mirror is configured by a reflective mirror thatconverts by 90 degrees the optical axis of the excitation lighttransmitted by the transmissive portion of the light emitting plate,wherein the fourth optical axis converting mirror is configured by areflective mirror that converts by 90 degrees the optical axis of theexcitation light converted by the second optical axis converting mirror,and wherein the third optical axis converting mirror is configured by adichroic mirror that converts by 90 degrees the optical axis of theexcitation light converted by the fourth optical axis converting mirrorwithout changing the optical axis of the fluorescent light converted bythe first optical axis converting mirror.
 11. The device according toclaim 6, wherein the second to fourth optical axis converting mirrorscomprise three reflective mirrors that convert the optical axis of theexcitation light.
 12. The device according to claim 1, wherein the lightemitting plate is formed to have a disc shape and provided with a driveunit that rotates the light emitting plate in a circumferentialdirection.
 13. The device according to claim 1, wherein the opticaldevice comprises a plurality of reflective mirrors and a dichroicmirror.
 14. A projector comprising: a light source device according toclaim 1; a display element; a first optical system that guides lightfrom the light source device to the display element; a second opticalsystem that projects an image emitted from the display element onto ascreen; and a projector controller that controls the light source deviceand the display element.